Interpretive Summary: Young pigs have a high requirement for arginine due to its utilization by multiple metabolic pathways. However, arginine intake from sow’s milk is low relative to the need for protein deposition in growing piglets. Therefore, ARS scientists within the Livestock Issues Research Unit in Lubbock, Texas, collaborated with a swine nutritionist at Texas Tech University to determine if supplementing arginine in the diets for gilts during gestation and lactation would stimulate milk production and thus the weight gain of sow-reared piglets. Results from this study revealed that supplementing dietary arginine to lactating sows enhanced the growth performance of suckling piglets. The information gained from this study will be of particular interest to swine producers, feed ingredient companies, and scientists working in the area of nutritional supplements to improve productivity in domestic livestock.

Technical Abstract:
A 2 x 2 factorial arrangement of treatments in a randomized block design was utilized to determine the effects of dietary arginine supplementation during gestation and/or lactation on the lactation performance of 38 first-parity sows. At 30 d of gestation, pregnant gilts were allotted based on BW to one of two diets supplemented with 1% L-arginine-HCl or 1.7% L-alanine (isonitrogenous control). After farrowing, sows were further allotted based on BW within previous gestation treatment groups to one of two lactation diets supplemented with 1% L-arginine-HCl or 1.7% L-alanine (isonitrogenous control). All gestation diets contained 3.1 Mcal/kg and 12.2% CP and were fed 2 kg/d in two equal-sized meals, whereas all lactation diets contained 3.2 Mcal/kg and 18.6% CP and were fed ad libitum. Litter size was standardized to a minimum of 9 piglets by cross-fostering within 24 h post-farrowing, depending on piglet availability. On a weekly basis, BW and BF thickness of sows, as well as piglet BW, were measured, and blood and milk samples were obtained from sows. Days for return-to-estrus and ADFI were also recorded. There were no differences (P > 0.05) in BW, BF thickness, ADFI, or days of return to estrus among treatment groups. On d 7 of lactation, plasma concentrations of arginine and insulin in sows, as well as concentrations of most amino acids in milk were higher (P < 0.05) in response to arginine supplementation during lactation compared to the control. Weight gain of piglets from sows fed the arginine-supplemented diet during lactation was higher between d 0 and 7 (P < 0.01) and between d 0 and 21 (P < 0.05) of lactation, compared to piglets from sows fed the control diet. Weight gains for litters from sows fed the arginine-supplemented diet during lactation were greater between d 0 and 7 (P < 0.01) and tended to be greater between d 0 and 21 (P = 0.058) of lactation, in comparison with the control. Collectively, results from this study indicate the potential beneficial effects of dietary arginine supplementation in improving the lactation performance of first parity sows.